AD9753-EB(Rev0) View Datasheet(PDF) - Analog Devices

Part Name

Description

Manufacturer

AD9753-EB
(Rev.:Rev0)

12-Bit, 300 MSPS High-Speed TxDAC+® D/A Converter

Analog Devices

AD9753-EB Datasheet PDF : 26 Pages

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AD9753

DVDD AVDD

CLK+ CLK– PLLLOCK

PLL/DIVIDER

PORT 1

DATA

INPUT

LATCHES

IOUTA

DAC

PORT 2

DATA

INPUT

FSADJ

INPUT

LATCHES

IOUTB

AD9753

RSET2

1.9k⍀

REFIO ACOM1 ACOM DCOM

0.1␮F

50⍀

0.1␮F

68⍀ 68⍀

INPP

INPM

OUTP

OUTM

LOIM

LOIP

AD8343 ACTIVE MIXER

LOINPUT

0.1␮F

M/A-COM ETC-1-1-13 WIDEBAND BALUM

Figure 30. QAM Transmitter Architecture Using AD9753 and AD8343 Active Mixer

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MARKER 1 [T2]

RBW 10kHz RF ATT 0dB

–99.88dBm VBW 10kHz

859.91983968MHz SWT 2.8 s UNIT

dBm

1 [T2]

–99.88bBm,

+859.91983968MHz

CH PWR

–65.67dBm

ACP UP

–65.15dBm

ACP LOW

–7.05dBm

1 [T2]

33.10dB

–49.91983968MHz

2 [T2]

33.10dB

–49.91983968MHz

2MA

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C11

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CENTER 860MHz

11MHz/

Cu1

SPAN 110MHz

COMMENT A: 25 MSYMBOL, 64 QAM CARRIER @ 825MHz

Figure 31. Signal of Figure 28 Mixed to Carrier

Frequency of 800 MHz

Effects of Noise and Distortion on Bit Error Rate (BER)

Textbook analysis’ of Bit Error Rate (BER) performance are

generally stated in terms of E (energy in watts-per-symbol or

watts-per-bit) and NO (spectral noise density in watts/Hz). For

QAM signals, this performance is shown graphically in Figure

32. M represents the number of levels in each quadrature PAM

signal (i.e., M = 8 for 64 QAM, M = 16 for 256 QAM). Figure

32 implies grey coding in the QAM constellation, as well as the

use of matched filters at the receiver, which is typical. The hori-

zontal axis of Figure 32 can be converted to units of energy/

symbol by adding to the horizontal axis 10 log of the number of

bits in the desired curve. For instance, to achieve a BER of 1e-6

with 64 QAM, an energy per bit of 20 dB is necessary. To cal-

culate energy per symbol, we add 10 log(6), or 7.8 dB. 64 QAM

with a BER of 1e-6 (assuming no source or channel coding) can

therefore theoretically be achieved with an energy/symbol-to-

noise (E/NO) ratio of 27.8 dB. Due to the loss and interferers

inherent in the wireless path, this signal-to-noise ratio must be

realized at the receiver to achieve the given bit error rate.

Distortion effects on BER are much more difficult to determine

accurately. Most often in simulation, the energies of the stron-

gest distortion components are root-sum-squared with the noise,

and the result is treated as if it were all noise. That being said, if

the example above of 64 QAM with the BER of 1e-6, using the

E/NO ratio is much greater than the worst-case SFDR, the noise

will dominate the BER calculation.

The AD9753 has a worst-case in band SFDR of 47 dB at the

upper end of its frequency spectrum (see TPCs 4, 7). When

used to synthesize high-level QAM signals as described above,

noise, as opposed to distortion, will dominate its performance in

these applications.

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4 QAM 16 QAM

64 QAM

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SNR/BIT – dB

Figure 32. Probability of a Symbol Error for QAM

REV. 0

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